In the history of electronic music, the Theremin stands alone. To this day, it remains the first and only instrument of its kind that can be played without any physical contact from the performer. Its eerie sounds were used in the 1930s by the symphony orchestras of New York, Philadelphia and Cleveland, and by the 1970s it had found a place in popular music—showing up on songs by Led Zeppelin and the Rolling Stones. Invented by Russian physicist Leon Theremin (1896 – 1993), this particular Theremin was manufactured by RCA as part of a pilot run of approximately 500 units in 1929.